title: History assignment: when was the mitochondrion founded?
abstract: The near simultaneous radiation of the major eukaryotic evolutionary assemblages-plants, animals, fungi, and at least three other complex protist assemblages worthy of 'kingdom level' status-was preceded by the divergence of many independent protist lineages. The earliest branches are represented by organisms that do not contain mitochondria or plastids, suggesting that the primitive eukaryotic state did not include these organelles. New information about nuclear-coded proteins that localize in the mitochondrion, however, suggests that the ancestral symbionts for mitochondria were present in the first eukaryotes. Phylogenetic support for this hypothesis is persuasive but it is not possible to account for the relative times of divergence for mitochondria and their ancestral symbionts relative to eukaryotic branching patterns inferred from nuclear genes.
authors.affiliation: Marine Biological Laboratory, Woods Hole, Massachusetts 02543, USA. sogin@mbl.edu
authors.forename: M l
authors.initials: Ml
authors.lastname: Sogin
mesh_terms: D000818:Animals; D005075:Biological Evolution; D002467:Cell Nucleus / Q000235:genetics; D005057:Eukaryotic Cells; D016678:Genome; D006360:Heat-Shock Proteins / Q000235:genetics; D008928:Mitochondria / Q000235:genetics; D010802:Phylogeny; D013559:Symbiosis
chemical_list: D006360:Heat-Shock Proteins